In the past, column chromatography has been used for the separation of many kinds of multicomponent solutions using a column packed with a solid absorbent which selectively adsorbs the components such as an ion exchange resin or a molecular sieve.
In recent years, such column chromatography has been increasingly used on a large scale in many industrial fields, for example, in the food industrial field for the separation of fructose and glucose from invert sugar solutions or high fructose corn syrup solutions by using cation exchange resins in the calcium form, for the separation of maltose and beta-limit dextrin from starch hydrolyzates, in the petroleum industrial field for the separation of normal-paraffins and iso-paraffins by using a solid absorbent containing aluminosilicate, and in other industries for the recovery of copper and ammonium, separation of nucleic acid, softening water, and recovery of glutamic acid, etc.
However, the following problems arise when conducting industrial chromatographic separation processes on a large scale.
(1) The length of the column must be long enough to enable sufficient separation of the soluble components, but there are some restrictions in using a long column for feasible industrial separation; therefore, it is necessary that the feed solution containing multiple components can be separated into pure separate components by using a relatively short length column.
(2) Generally, dilution of separated soluble components with desorbent cannot be avoided.
Especially in the conventional batchwise process of chromatographic separation, the leading edge portion and the tailing edge portion of a separation zone are diluted; accordingly each fraction which contains a completely recovered component is too dilute, causing the disadvantage of having to remove desorbent from each fraction by evaporation, which requires a large amount of fuel and high operating costs.
Heretofore, to solve those problems mentioned above several methods have been provided. One of those methods, the simulating moving bed process (Japanese Patent Publication No. 51-18,392 or Japanese Patent Open-Laid No. 51-101,140) has the following disadvantages: the column must have a very complex structure and the operation of this process requires technically highly complicated control by using a computer. Another method, the moving bed system (Japanese Patent Publication No. 46-18214) has several problems such as difficulty in moving adsorbent without disturbance of separation and also the reliability of separation is questionable.